The present invention relates generally to data processing systems and more particularly to the terminal and input/output control sections of a data processing system.
In data processing systems the terminal is normally connected to the system (host) central processing unit (CPU) through an RS232 cable. A CRT display, a keyboard and sometimes a mouse are connected to the terminal. Control of these devices is achieved though a controller device in the terminal. The controller device usually includes some logic and/or hardware for generating the video timing and control signals for the CRT display. The video memory for use with the CRT is generally a part of the controller devices. Input/output devices, such as a disk drive and/or a tape drive are connected to the system input/output bus, each through a separate controller device having a separate processor.
One of the shortcomings of this arrangement is that it uses a number of different processors, one for the terminal controller and a separate one for each one of the input/output controllers. Another shortcoming of this arrangement is that although the memory in the terminal controller is generally adequate for use with the CRT display for displaying text it is not adequate when graphics are to be displayed.
It is an object of this invention to provide a new and improved data processing system.
It is another object of this invention to provide a new and improved I/O controller for a data processing system.
It is still another object of this invention to provide a new and improved video control section for a data processing system.
It is yet still another object of this invention to provide a data processing system in which the video memory is connected directly to the system memory bus.
It is another object of this invention to provide a data processing system in which all of the input/output control devices are managed by a single processor.